1. Field of the Invention
The present invention relates generally to a label printer widely used in the field of, e.g., POS (point of sale), FA (factory automation), physical distribution or the like. More particularly, the present invention relates to a label printer having an ink jet printing system employed therefor.
2. Description of the Related Art
A label printer having an ink jet printing system utilized therefor has not been put in practical use till now. General advantages obtainable from ink jet recording are as noted below. Specifically, one of them is that ink jet printing is effected with excellent quietness attributable to no contact with a printing medium, another one is that ink jet printing is performed at a high speed, another one is that ink jet printing can be achieved at a high density, a further one is that ink jet color printing can easily be realized, and an ink jet printing apparatus can be designed with small dimensions.
A conventional label printer is usually constructed such that so-called label paper unwound from a roll is conveyed through a printing section, and the roll is prepared in such a manner that a number of labels are successively adhesively placed on a long peeling sheet that is called a separator in the equally spaced relationship. In the case that the ink jet system is applied to the label printer of the foregoing type, it is required to take a measure for suppressively preventing the label paper from being floated up at a printing head, and moreover, being slantwise conveyed.
Lately, there is a tendency that the number of bar codes becomes short. For this reason, colored bar code is taken into account. In this circumstance, it is advantageous to employ the ink jet system. In the case that a color label printer is designed, when a printing speed is set to a high level, a printing signal to be applied to each color printing head has an increased frequency, causing a necessity to arise for enlarging the capacity of a driving power source. This leads to problem that a size of the power source is enlarged, and the color label printer is produced at an increased cost.
In the case that the ink jet system is employed for a label printer and the label printer is left unused for a long time, to prevent ink from being unstably ejected, it is advantageous that ink present in the vicinity of a printing head is caused to recirculate with the aid of a so-called recovering system. A recovering operation is generally achieved by bringing a recovering unit in contact with or in close vicinity to a printing head that is printing means. However, since roll-shaped label paper is usually used for the label printer, there does not arise an occasion that the paper to be printed disappears from the printing position. Therefore, in contrast with a printer operable with cut printing papers like an ordinary office-use printer, it is very difficult to arrange a recovering system and design a recovering sequence.
In this connection, it is also very difficult to compactly design and construct a printing head, a recovering system unit, an ink feeding system, and a printing medium conveying system.